This invention relates to a luminaire having a reflector structure which mixes light from a multi-color array of LEDs, and more particularly to such luminaire which mixes light to generate a white light spotlight from such an array.
The standard light source for small to moderate size narrow beam lighting for accent lighting and general illumination is the incandescent/halogen bulb, such as a PAR (parabolic aluminized reflector) lamp. These light sources are compact and versatile, but they are not very efficient. A given lamp operates at a given color temperature for a fixed power, and while they are dimmable, the color temperature shifts with the level of applied power according to the blackbody law, which may or may not be the variation that the user desires.
An array of LEDs in each of a plurality of colors offers the possibility of creating a luminaire in which the color temperature may be controlled at any power level, thereby enabling a lamp which is dim able and emits a uniformly white light at any power level.
Our co-pending application Ser. No. 09/277,645, filed Mar. 26, 1999, now U.S. Pat. No. 6,200,002B1 issued Mar. 13, 2001, titled xe2x80x9cLuminaire Having A Reflector For Mixing Light From A Multi-Color Array of LEDsxe2x80x9d, is assigned to the same assignee as the present application, and the disclosure thereof is hereby incorporated in this application by this reference thereto. The application indicates that the problem encountered with a luminaire structure design that uses red, green, and blue LEDs and a reflector structure to make color-controllable white-light spotlights suitable for accent lighting and general illumination is mainly to get good color mixing and still keep the total transmission efficiency high, and the beam narrow and well controlled. Said co-pending application achieves good mixing with improved results when compared to the prior art with a structure wherein a light source which includes an array of LEDs in each of a plurality of colors such as red, green, and blue, is provided in the entrance aperture of a tubular reflector which preferably has convex walls facing the optic axis and flares outward toward the exit aperture, and preferably has a polygonal cross section such as a square. In a preferred embodiment of the invention disclosed and claimed in said co-pending application, the light source utilizes an array of LEDs, including at least one LED in each of a plurality of colors, for emitting light in each of the plurality of colors. The array is arranged in the entrance aperture of a reflecting tube having an opposed exit aperture from which light is emitted after being reflected and mixed by a circumferential wall extending between the apertures.
The light source has an optic axis extending between said apertures centrally of the circumferential wall, and a cross-section transverse to the axis. The cross-section is preferably non-round along at least part of the optic axis and is preferably polygonal along the entire length of the axis. Square and octagonal cross-sections are used for mixing light from the various colors. Most notably, the circumferential wall diverges from the entrance aperture to the exit aperture, and the exit aperture is larger than the entrance aperture. The circumferential wall, seen from the optic axis preferably has a convex shape and flares outward toward the exit aperture. That is the radius of curvature of the wall decreases toward the exit aperture, making the reflector somewhat horn-shaped. We refer to such a structure as a xe2x80x9chornxe2x80x9d luminaire because of its generally flared shape. Our horn luminaire has a planar array of LEDs that sit at specified positions within an input aperture, and the emitted light from the various colors is mixed by several reflections from concave-curved walls. In general, in most embodiments of the horn luminaire, some provision must be made to direct the LED light into an initial cone of about 2xc3x9760xc2x0 before the light is incident on the main reflective walls of the horn. The horn luminaire provides the desirable features of a PAR lamp, plus independent color-temperature and dimming control, all at greater luminous efficacy than a PAR lamp. Moreover, the horn luminaire employs a set of red, green and blue LEDs, to make uniform white light in a relatively narrow to moderate beam.
There is still, however, a need in the art for a light source that comprises a luminaire that is effective as the LED package as well as the optical element, and where the reflector body can accept the full 2xc3x9790xc2x0 emission of the array of LED chips without any provision for xe2x80x9cprimary opticsxe2x80x9d close to the individual LEDs.
An object of the present invention is to provide a light source which comprises a tubular reflector which is effective as the LED package as well as the optical element.
Another object of the invention is to provide a light source which comprises a reflector body that can accept the full 2xc3x9790xc2x0 emission of an array of LED components without the necessary provision for xe2x80x9cprimary opticsxe2x80x9d close to the individual LEDs.
These and other objects of the invention are accomplished, according to a description of the present invention that follows:
This invention in its preferred embodiments provides a white or color-controlled spotlight for general illumination and accent lighting, using red, green, and blue LEDs, and especially LED chips as sources.
This invention is an alternative to the horn luminaire described and claimed in our said co-pending application Ser. No. 09/277,645 referred to above. As in the invention of said co-pending application, according to the present invention also (a) an LED light source is provided that will provide all of the desirable features of PAR lamps, the ability to vary and control color temperature, at full power and when dimmed, all at greater luminous efficacy; (b) good color mixing is provided for an extended size of array of LEDs; and (c) a collimated beam of mixed light emerging from the light source is provided.
The preferred embodiment of the invention utilizes an array of LED chips which fills the entrance aperture of a reflector having a polygonal cross-section.
For an economically viable product, the requirements of high light output, good control over emission pattern, small size, high efficiency, and good color mixing in both the near field and the far field must be met and are met by the light sources of this invention.
According to the present invention, a white or color-controlled spotlight for general illumination and accent lighting, using red, green, and blue LED chips as sources is provided which meets the requirements stated above for an economically viable product. An improved reflector which is the LED package, i.e. the primary package for the LEDs, as well as the luminaire or optical element, is provided which in a first embodiment, has a polygonal cross-section taken normal to the optic axis, preferably a hexagonal or octagonal cross-section, and wherein at least a portion of the circumferential body, and (i.e., the reflector walls) comprises or is defined by planar trapezoidal segments or facets.
This invention provides a light source comprising:
an array of LED components comprising at least one LED component in each of a plurality of colors for emitting light in each of a plurality of colors and
a reflecting tube having an entrance aperture, an exit aperture, a reflective circumferential wall extending between said apertures, and an optic axis extending between said apertures centrally of said wall, said array of LED components being arranged in said entrance aperture, said reflective circumferential wall being arranged to reflect and mix light from said array of LED components, wherein the reflecting tube has a polygonal cross-section taken normal to the optic axis, preferably a hexagonal or octagonal cross-section, and wherein at least a portion of the circumferential body comprises planar trapezoidal segments or facets.
The improved reflector can accept the full 180 degrees of emissions from the LED array, and there is more flexibility in the design of the output beam.